The UK's most complete GLP-1 guide
Every Question Answered. Every Side Effect Explained.
- How GLP-1 medications work
- Mounjaro vs Wegovy compared
- Injection instructions
- Side effects & solutions
- What to eat on treatment
- FAQs answered
Free tracker included with every download this week
Mounjaro 15mg: The Maximum Dose Explained
Mounjaro 15mg is the highest dose of tirzepatide available on prescription in the UK for weight management. This dose is typically reached after a gradual escalation process starting at 2.5mg, with increases every 4 weeks as tolerated. The 15mg dose represents the final maintenance level for adults who may benefit from the maximum therapeutic effect. Not everyone reaches this dose—your prescriber will assess whether dose escalation is appropriate for your individual health circumstances and tolerance.
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Enter your height and weight below. Supports both imperial (stone & lbs) and metric (kg). Results include NHS category, healthy weight range, and ethnicity adjustments.
What Is BMI and Why Does It Matter?
Body Mass Index (BMI) is the most widely used screening tool for assessing whether your weight falls within a healthy range. Used by the NHS, GPs, and weight management services across the UK, BMI provides a quick snapshot of your weight relative to your height. The formula is simple: your weight in kilograms divided by your height in metres squared (kg/m²).
While BMI isn't a perfect measure — it doesn't account for muscle mass, bone density, or fat distribution — it remains the standard first step in identifying potential weight-related health risks including type 2 diabetes, cardiovascular disease, high blood pressure, and certain cancers.
The NHS also recommends adjusted thresholds for people of South Asian, Chinese, or Black African heritage — a BMI of 23 or above is classified as overweight, and 27.5 as obese. Our calculator includes this adjustment as a one-click toggle.
How Mounjaro Dosing Works in the UK
Mounjaro follows a structured dose escalation schedule rather than starting at the maximum. Each dose is a once-weekly injection via the pre-filled KwikPen device. The standard titration path is:
- Weeks 1–4: 2.5mg starting dose
- Weeks 5–8: 5mg (first escalation)
- Weeks 9–12: 7.5mg
- Weeks 13–16: 10mg
- Weeks 17–20: 12.5mg
- Week 21 onwards: 15mg maximum dose
Your prescriber may pause or repeat any dose level if side effects occur or if you're responding well at a lower dose. Reaching 15mg typically takes 5–6 months from treatment start. The tirzepatide mechanism works as a dual GIP and GLP-1 receptor agonist, helping regulate appetite and support weight management alongside reduced-calorie diet and increased physical activity.
Clinically BackedWeight Loss
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How It Works
Three simple steps to understand your weight and take action.
Enter your height and weight in our free calculator. Get your BMI, NHS category, healthy weight range, and ethnicity-adjusted thresholds instantly.
If your BMI suggests you're overweight or obese, explore our GLP-1 calculators to project potential weight loss on Mounjaro or Wegovy.
Use our progress tracker to log your weight weekly, visualise your journey with charts, and stay motivated — all stored privately in your browser.
Free Weight Loss Tools & Guides
Everything you need to understand your weight, explore medication options, and track your progress — completely free.
Expected Outcomes at the 15mg Dose
Clinical trial data (SURMOUNT-1) showed that participants on the 15mg dose achieved an average weight loss of approximately 20.9% of their body weight over 72 weeks—though individual results vary significantly. Some people may see meaningful results at lower doses and choose to remain on 10mg or 12.5mg. Your GP or prescriber will regularly assess whether the 15mg dose is right for you. Calculate your potential weight loss range using our GLP-1 weight loss calculator above. Monitor your progress with our free progress tracker to log results, side effects, and how you're feeling throughout treatment.
- Dual GIP/GLP-1 receptor agonist
- Up to 22.5% body weight loss (SURMOUNT-1)
- Weekly injection, dose escalation over 20+ weeks
- Available via private prescription in the UK
- Doses: 2.5mg → 5mg → 7.5mg → 10mg → 12.5mg → 15mg
- GLP-1 receptor agonist
- Up to 15–17% body weight loss (STEP trials)
- Weekly injection, 5-step dose escalation
- NHS & private prescription available
- Doses: 0.25mg → 0.5mg → 1mg → 1.7mg → 2.4mg
Mounjaro vs Wegovy: Head-to-Head
A side-by-side comparison of the two most popular GLP-1 weight loss medications available in the UK.
| Feature | Mounjaro | Wegovy |
|---|---|---|
| Drug class | Dual GIP/GLP-1 agonist | GLP-1 agonist |
| Active ingredient | Tirzepatide | Semaglutide |
| Avg. weight loss | 15–22.5% | 12–17% |
| Key trial | SURMOUNT-1 (2022) | STEP 1 (2021) |
| Max dose | 15 mg weekly | 2.4 mg weekly |
| Escalation period | 20–32 weeks | 16–20 weeks |
| Administration | Weekly injection (pen) | Weekly injection (pen) |
| NHS availability | Private prescription only | NHS & private |
| Approx. private cost | £150–£250/month | £150–£300/month |
| Common side effects | Nausea, diarrhoea, constipation | Nausea, vomiting, diarrhoea |
Data sourced from SURMOUNT-1 and STEP 1 clinical trials. Costs are approximate and vary by provider. Always consult a prescriber.
Am I Eligible for Weight Loss Medication?
In the UK, eligibility for GLP-1 weight loss medications like Mounjaro and Wegovy is based on your BMI and overall health profile.
- BMI of 30 or above (obese)
- Age 18 or over
- No contraindicated conditions
- Committed to lifestyle changes
- BMI of 27 or above
- Plus type 2 diabetes
- Or high blood pressure
- Or obstructive sleep apnoea
Use our BMI calculator to check whether your BMI falls within the eligible range.
How We Built These Tools
Every calculator and guide on myweightcheck is built with accuracy and transparency in mind. Our BMI calculator uses the standard WHO formula with NHS-aligned category thresholds. Our GLP-1 projections are modelled on published clinical trial data from SURMOUNT and STEP studies.
All data stays on your device. We don't require sign-ups, and we don't store your health information on any server. Your progress tracker saves data locally in your browser using localStorage, so only you can see it.
We're based in the UK and our tools are designed specifically for UK users — supporting stone & lbs by default, referencing NHS guidelines, using NICE-approved medication data, and linking to GPhC-registered pharmacies.
Frequently Asked Questions
Common questions about BMI, weight loss medications, and our free UK tools.
How long does it take to reach the Mounjaro 15mg dose?
The standard escalation schedule takes approximately 5–6 months to reach 15mg from the starting dose of 2.5mg. Each dose level lasts a minimum of 4 weeks. Your prescriber may adjust this timeline based on side effects or individual response.
Will I definitely need to escalate to the 15mg maximum dose?
No. Your prescriber will assess whether escalation is appropriate for you. Some people respond well at lower doses (5mg, 10mg, or 12.5mg) and may not need or benefit from reaching 15mg. Treatment is individualised based on tolerance and effectiveness.
Is Mounjaro 15mg available on the NHS in the UK?
Mounjaro is available through NHS specialist weight management services (tier 3/4). Access varies significantly by region. Many areas have long waiting lists. Private prescription access is also available through GPhC-registered online pharmacies following a clinical assessment.
What are the side effects at the 15mg dose?
Common side effects include nausea, diarrhoea, constipation, and stomach pain—typically lessening over time. Serious side effects are rare but include severe stomach pain (possible pancreatitis) and allergic reactions. Always report new or worsening symptoms to your GP.
Can I switch from Wegovy to Mounjaro at 15mg?
Switching between medications should only be done under prescriber guidance. Approximate equivalence suggests Wegovy 2.4mg is roughly equivalent to Mounjaro 10–15mg, but there is no official conversion chart. Your prescriber will decide the safest approach for your individual situation.
Ready to take control of your weight loss journey?
Start with a free BMI check, explore your GLP-1 options, or begin tracking your progress today. No sign-up. No cost. Just results.